This invention relates generally to downhole drilling tools and more particularly to an adjustable bent housing for use with a mud motor for directional drilling.
Mud motors are used in downhole drilling operations to effect drilling at the bottom of the hole without rotating the drill string. Such mud motors are driven by fluid pressure. Directional drilling using mud motors is achieved by placing a subsection of the drill string tubing, adjacent the mud motor, with a central bore that is offset to the central axis of the drill string to deviate the borehole from vertical to a desired angle. Such subsections are referred to as xe2x80x9cBent housingsxe2x80x9d. These xe2x80x9cbent housingsxe2x80x9d are short sections of pipe or tubing either internally or externally threaded at each end and are xe2x80x9cbentxe2x80x9d either by physical bending or machined to create an angular offset between the respective ends of the housing. When the xe2x80x9cbent housingxe2x80x9d is placed in the drill string, the bend in the housing causes the drill string to deviate from vertical as drilling progresses. More recently the industry has come to rely on a single bent housing on which the angle can be adjusted. The angle of the present housing is adjusted prior to insertion into the well and remains fixed until withdrawn and readjusted. Housings of this type are therefore referred to as xe2x80x9csurface adjustablexe2x80x9d bent housings to distinguish them from housings that are xe2x80x9cdownhole adjustablexe2x80x9d, that is, adjustable while in the well bore without being withdrawn to the surface.
Although the terms xe2x80x9csubsxe2x80x9d and xe2x80x9chousingsxe2x80x9d are sometimes used synonymously, a xe2x80x9csubxe2x80x9d is typically a bent section installed in the drill string above the downhole motor/bearing assembly/drill bit combination used in the directional drilling of well bores. A xe2x80x9chousingxe2x80x9d, on the other hand, fits between the motor and the bearing assembly and, in addition to providing bend, it also accommodates a drive shaft connecting the motor to the bearing assembly/drill bit through its central bore. The present invention is intended for use primarily as an adjustable bent xe2x80x9chousingxe2x80x9d.
The present invention represents an adjustable bent housing structure for downhole mud motor directional drilling operations. According to the present invention, there is provided an adjustable bent housing for a downhole mud motor that includes a cylindrical housing having a first and a second end defining a central bore there through, the housing being divided into first and second body members, the body members being axially offsetable to one another said first body member having a mandrel portion insertable along a portion of its length into the bore of the second body member with angularity between the first and second body members achieved by rotational displacement of a first outer sleeve, having non-parallel ends, disposed annularly about the mandrel, and a second inner eccentric sleeve, also disposed annularly about the mandrel, the inner sleeve having a locking member for connecting to the outer sleeve and being axially movable relative to the mandrel in response to rotation of the outer sleeve, and a setting means provided for securing the outer sleeve to prevent relative rotation between the outer collar and the first body member.